1. Field of the Invention
This invention relates to improvements in compression type crushers such as cone crusher, gyratory crusher and jaw crusher, and more particularly to a crusher with a crushing chamber of an improved shape which can attain a high reduction ratio.
2. Description of the Prior Art
The reduction rate in a closed circuit of conventional crushers is at most about 5 to 6 owing to overcompression or blocking of material in the crushing chamber. The term "reduction ratio" as used in this specification means the dimensional ratio of the material before and after the crushing operation. In order to obtain a product of a given size, it has been the usual practice in the conventional crushing plants to process the material progressively through a number of stages, e.g., through first to third crushing stages. The improvement of the reduction ratio is a matter of great importance to the compression type crusher since it will lead to the reduction of the operation time and the enhancement of the operational efficiency. The conditions for the improvement of the reduction ratio include the fact that: (1) the material should be subjected to sufficient crushing forces; (2) the maximum size of the product should be reduced; (3) a material of a large size can be fed through the inlet of the crushing chamber; and (4) the crushing chamber can be filled with the material, permitting the so-called choke feed to ensure stabilized operation and higher efficiency. In order to satisfy these conditions, it is necessary to design the crushing chamber to be of a shape with a broad inlet and a narrow outlet, which is, however, unsuitable for application to conventional crushers in consideration of the drop in the production speed and the overcompression which would result from blocking of the crushing chamber by the feed material. Further, the quantity and speed of the oscillatory movement of the crusher plate need to be determined with consideration of the behavior of the material in the crushing chamber, in appropriate ranges which are contributive to the enhancement of the reduction ratio, in relation to the shape of the crushing chamber.